Integrated mobile power unit for hydraulic fracturing

ABSTRACT

A hydraulic fracturing system is disclosed as including a singular mobile platform of at least one mobile power unit (MPU) and at least one first switch gear that is configured to handle electric power from the MPU. The MPU is configured to generate voltage that matches the capabilities of an electrical bus from the at least one switch gear such that a combined electrical current generated as a result of the generated voltage and required load is provided to the electrical bus to the components of the hydraulic fracturing system. Further, the hydraulic fracturing system may include electrical fracturing equipment with at least one second switch gear to support the at least one first switch gear in handling electric power from the MPU. A datavan may be included in the system to control load shedding, load sharing, and power distribution for the electrical fracturing equipment comprising the at least one second switch gear.

RELATED APPLICATION

The present disclosure is related to and claims priority from U.S.Provisional Application 62/685,797, titled INTEGRATED MOBILE POWER UNITFOR HYDRAULIC FRACTURING, filed on Jun. 15, 2018, the entirety of thedisclosure of which is incorporated by reference herein.

BACKGROUND 1. Field of Invention

The present disclosure generally relates to hydraulic fracturing. Inparticular, the present disclosure relates to mobile grid assembly forpowering an electric hydraulic fracturing pump in limited spaceenvironments.

2. Related Technology

Fracturing, such as hydraulic fracturing, stimulates production fromhydrocarbon producing wells. Such a process may utilize mobile systemsfor injection of fluid into wellbores at pressure to providesubterranean fissures in the area around the wellbores. Such a processrelies on fracturing fluid slurry that has been pressurized using highpressure pumps. As this is a mobile process, the high pressure pumps aremounted on mobile surfaces—e.g., truck-beds, trailers, etc. Moreover,the high pressure pumps are powered by mobile power sources, such asdiesel engines. However, the components, such as the high pressure pumpsand associated power sources have large volume and mass. As such, themobile surfaces may be heavy duty trailers, trucks, or skids that areused for transporting these components to remote sites where wellboresare being fractured. The components support hydraulic fracturing pumpsthat draw low pressure fluid slurry (at approximately 100 psi). Thedischarge of the same fluid slurry, however, is at high pressures of upto 15,000 psi or more. In addition, alternate mobile power sources, suchas turbine generators, are available to perform the power functions ofthe diesel engines. At the remote site, the power sources areelectrically connected to power the fracturing components. For example,motors for pressurizing fracturing and hydraulic fluids are connected tothe power sources using power buses. Electrical connections may becomplex, unsafe, unreliable, and may include numerous configurationsrequiring space and time to resolve.

SUMMARY

Herein disclosed are examples of a hydraulic fracturing system thatincludes a singular mobile platform of at least one mobile power unit(MPU) and at least one first switch gear that is configured to handleelectric power from the MPU. The at least one MPU is configured togenerate voltage that matches the requirements of load and an electricalbus of the at least one first switch gear, such that a combinedelectrical current generated as a result of the generated voltage isprovided through the electrical bus to the components of the hydraulicfracturing system. Further, the hydraulic fracturing system may includeelectrical fracturing equipment with at least one second switch gear tosupport the at least one first switch gear in handling electric powerfrom the at least one MPU. Automated control software may be included inthe system to control load shedding, load sharing, and powerdistribution for the electrical fracturing equipment comprising the atleast one second switch gear. In addition, the switchgear may beseparate units or incorporated into the MPUs. Fracturing equipment,including the electrical load, may include specific voltage and currentrequirements. The electrical bus is, therefore, sized to match the MPU'scapabilities based on the load requirements. Electrical buses may berated in terms of maximum capability before failure, such as a voltageclass of 5000V, 15000V, or 25000V, and having a current rating such as1200 A, 2000 A, or 3000 A.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the features and benefits of the present invention having beenstated, others will become apparent as the description proceeds whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic of an example hydraulic fracturing system inaccordance with embodiments of the present disclosure.

FIG. 2 is an elevation schematic of example portions of an MPU,including at least a turbine, generator, and EER in one or moretrailers.

FIG. 3 is an end perspective view of an example of a mobile platformthat includes one or more mobile power units (MPUs) that is integratedto or with switch gear components, according to embodiments in thepresent disclosure.

FIG. 4 is an elevation schematic of portions of the hydraulic fracturingsystem in accordance with one example configuration of the embodimentsherein.

FIG. 5 is an elevation schematic of portions of a hydraulic fracturingsystem in accordance with another example configuration of theembodiments herein.

FIG. 6 is an elevation schematic of portions of a hydraulic fracturingsystem in accordance with yet another example configuration of theembodiments herein.

FIG. 7 is an elevation schematic of portions of a hydraulic fracturingsystem in accordance with further example configurations available usingthe embodiments herein.

FIG. 8 is an elevation schematic of portions of a hydraulic fracturingsystem according to other example configurations of the embodimentsherein.

FIG. 9 is an elevation schematic of portions of a hydraulic fracturingsystem according to other example configurations of the embodimentsherein.

FIG. 10 is an elevation schematic of portions of a hydraulic fracturingsystem according to other example configurations of the embodimentsherein.

FIG. 11 is a flowchart of a hydraulic fracturing method using theexample configurations of the embodiments herein.

While the invention will be described in connection with the preferredembodiments, it will be understood that it is not intended to limit theinvention to that embodiment. Instead, the preferred embodiments areintended to cover all alternatives, modifications, and equivalents, asmay be included within the spirit and scope of the invention as definedby the appended claims

DETAILED DESCRIPTION OF THE DISCLOSURE

So that the manner in which the features and advantages of theembodiments of hydraulic fracturing system and associated methods, aswell as others, which will become apparent, may be understood in moredetail, a more particular description of the embodiments of the presentdisclosure briefly summarized previously may be had by reference to theembodiments thereof, which are illustrated in the appended drawings,which form a part of this specification. It is to be noted, however,that the drawings illustrate only various embodiments of the disclosureand are therefore not to be considered limiting of the presentdisclosure's scope, as it may include other effective embodiments aswell.

The method and system of the present disclosure will now be describedmore fully hereinafter with reference to the accompanying drawings inwhich embodiments are shown. The method and system of the presentdisclosure may be in many different forms and should not be construed aslimited to the illustrated embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey its scope to those skilled in the art.Like numbers refer to like elements throughout. In an embodiment, usageof the term “about” includes +/−5% of the cited magnitude. In anembodiment, usage of the term “substantially” includes +/−5% of thecited magnitude.

It is to be further understood that the scope of the present disclosureis not limited to the exact details of construction, operation, exactmaterials, or embodiments shown and described, as modifications andequivalents will be apparent to one skilled in the art. In the drawingsand specification, there have been disclosed illustrative embodimentsand, although specific terms are employed, they are used in a genericand descriptive sense only and not for the purpose of limitation.

One system and method for powering electrical equipment from a generatoruses a physically separate mobile unit with switch gear installed to actas an electrical distribution hub between the MPUs and electricfracturing equipment of a hydraulic fracturing system. The separatemobile unit is, therefore, physically external relative to a mobile unithosting the generator and switch gear, for instance. In such animplementation, cables are used to supply power from the MPUs to themobile switch gear unit and between the mobile switch gear unit to theelectric fracturing equipment. Here, fleet wide load sharing and loadshedding are available, but such an implementation requires more mobileequipment and power cables. Alternatively, another system and methoduses a smaller and less versatile Electronic Equipment Room (EER), withswitch gear for the generator, to directly power a small amount ofelectric equipment. Such a system and method may require lesser physicalequipment, but is also electrically limited. For example, suchlimitations may be for load sharing and load shedding, which may belimited to only the equipment being supplied by a single MPU.

The present embodiments, by at least an MPU working with the switch gearin a single platform or unit resolves the additional issues noted abovewith the system and methods for a physically separate (e.g., external)mobile unit and an EER. For example, the present implementation at leastensures that MPUs are configured with adequate bus work to carry thegenerated voltage and current from the MPU's generator. This is furthersupported by the single platform or unit with reduced cabling andcomplexity with the MPU sharing space with the switch gear, forinstance. The present implementation works with well sites where spaceis limited and rapid mobilization and demobilization is required. Withintegrated components on a single skid, for example, fewer physicalconnections are needed to be established or stowed duringtransportation. In an example, mobilization and demobilization of asingle MPU are then limited to oilfield functions, such as pump downjobs, injection testing, toe preps, low hydraulic horsepower jobs, or tosupplement other equipment types (diesel, dual fuel). In addition, extraMPUs and pumps can be used to perform fracturing jobs with highhydraulic horsepower requirements.

Furthermore, the use of integrated switch gear with the MPU eliminatesthe need for a separate switch gear trailer or skid. This allows forfewer trailers and fewer interconnecting cables saving space and timeduring mobilization/demobilization. With fewer trailers and cables,capital and maintenance costs are also beneficially addressed by thepresent implementation. The method of equipment deployment, in thepresent implementation, is also modular and scalable as turbines of theMPU can be added to directly to power the electric fracturing pumps asneeded without the need to add additional switch gear trailers or modifyexisting trailers with additional gear and cable connections. Acomplexity sought to be addressed herein is a difficulty to implement acommon bus where much of the equipment is on the same circuit. As such,the common bus of the present disclosure supports the voltage andcombined current requirements of the various equipment loads. Atfracturing sites, fracturing pumps may be inoperable because of fluiddistribution problems, mechanical problems, communication problems,control problems, pump problems, sensor problems, etc. While these areunrelated to the electric power generation requirements discussedherein, without a common electrical bus, excess power from a turbinegenerator cannot be redistributed to other equipment which will limitredundancy in equipment and may cause situations where extra turbinesand fracturing pumps will need to be on standby in the event offailures. Other oilfield equipment may be connected to the commonelectrical bus. In an example, the other oilfield equipment includesintensifier pumps, blenders, dual blenders, hydration units, chemicaladditive units, data van, sand equipment, lights, CNG equipment, LNGequipment, gas compression, gas filtration, wireline, water transfer,flow back, coil tubing, nitrogen, cementing, dual pumper, drilling rigs,cranes, and workover rigs. There may also be a case where, when aturbine generator fails, the fracturing pumps or other equipment whichare electrically tied to it will be rendered inoperable and power willnot be available from other generators due to a lack of a common bus forpower distribution. As such, the present implementation overcomes theseadditional issues by load sharing switch gear added to the MPUs in thesame trailer or to other connected equipment, but working with theswitch gear of the MPUs as discussed throughout this disclosure.

One of ordinary skill would recognize that there are space constraintsof mobile equipment. As such, the turbine engine and generators of theMPU in the present implementation may need to be smaller to accommodatethe extra integrated switch gear. The reduction in size and capabilitycan create situations where extra MPUs will be needed on well sites withhigher hydraulic horsepower requirements. However, to save space andweight, alternative engines and generators may be used (such asaeroderivative turbines or reciprocating engines). Many light andcompact turbines may also struggle to burn wide ranges of fuel gas andmay need support equipment if the upper or lower heating values are outof the required range, but with the present implementation, redundanciesare widely applied to assist with any of these constraints.

The present disclosure, in an embodiment, is to a system including amobile unit, at least one generator; and at least one switch gear. Theat least one generator is coupled to the at least one switch gear on themobile unit forming a singular and integrated mobile unit. The mobileunit is configured to provide power generated by the at least onegenerator in electrical buses for at least one load on one or moreexternal mobile unit. In another embodiment, a method is disclosed andincludes providing a mobile unit with at least one generator and atleast one switchgear, such as a system as described above. The at leastone generator is coupled to the at least one switch gear on the mobileunit. The method includes generating power from the at least onegenerator and providing the power in electrical buses for at least oneload in one or more external mobile units. The system may be part of ahydraulic fracturing system that consumes the power and that includes awellbore and at least one pressuring system to create fractures in asubterranean formation that surrounds the wellbore.

FIG. 1 is a schematic of an example hydraulic fracturing system 10 inaccordance with embodiments of the present disclosure. Such a system maybe used for pressurizing a wellbore 12 to create fractures 14 in asubterranean formation 16 that surrounds the wellbore 12. System 10 mayinclude a hydration unit 18 that receives fluid from a fluid source 20via line 22, and may also receive additives from an additive source 24via line 26. Additive source 24 can be separate from the hydration unit18 as a stand-alone unit, or can be included as part of the same unit asthe hydration unit 18. The fluid, which in one example is water, ismixed inside of the hydration unit 18 with the additives. The fluid andadditives are mixed over a period of time to allow for uniformdistribution of the additives within the fluid.

In the example of FIG. 1, the fluid and additive mixture is transferredto a blender unit 28 via line 30. A proppant source 32 containsproppant, which is delivered to the blender unit 28 as represented byline 34, where line 34 can be a conveyer. Inside the blender unit 28,the proppant and fluid/additive mixture are combined to form afracturing slurry, which is then transferred to a fracturing pump system36 via line 38; thus fluid in line 38 includes the discharge of blenderunit 28 which is the suction (or boost) for the fracturing pump system36. Blender unit 28 can have an onboard chemical additive system, suchas with chemical pumps and augers (not shown). Optionally, additivesource 24 can provide chemicals to blender unit 28; or a separate andstandalone chemical additive system (not shown) can be provided fordelivering chemicals to the blender unit 28. In an example, the pressureof the slurry in line 38 ranges from around 80 psi to around 120 psi.The pressure of the slurry can be increased up to around 15,000 psi bypump system 36. A motor 39, which connects to pump system 36 viaconnection 40, drives pump system 36 so that it can pressurize theslurry.

In one example, the motor 39 is controlled by a variable frequency drive(“VFD”). After being discharged from pump system 36, slurry is injectedinto a wellhead assembly 41; discharge piping 42 connects discharge ofpump system 36 with wellhead assembly 41 and provides a conduit for theslurry between the pump system 36 and the wellhead assembly 41. In analternative, hoses or other connections can be used to provide a conduitfor the slurry between the pump system 36 and the wellhead assembly 41.Optionally, any type of fluid can be pressurized by the fracturing pumpsystem 36 to form a fracturing fluid that is then pumped into thewellbore 12 for fracturing the formation 14, and is not limited tofluids having chemicals or proppant. Examples exist wherein the system10 includes multiple pumps 36, and multiple motors 39 for driving themultiple pumps 36. Examples also exist wherein the system 10 includesthe ability to pump down equipment, instrumentation, or otherretrievable items through the slurry into the wellbore.

FIG. 1 additionally provides an example turbine 44, which receives acombustible fuel from a fuel source 46 via a feed line 48. In anexample, the turbine is part of a Mobile Power Unit (MPU) or platform.The MPU may be a trailerized, bodyload, or skid mounted electrical powergeneration unit which can use the turbine or reciprocating engine forpower generation. Such a turbine or reciprocating engine can be fueledby the combustible fuel, such as diesel or natural gas, to function asan electrical generator. The MPU can comprise of one or more trailers,composed of the generator, the electrical switching gear, a prime mover(engine), auxiliary loads (cooling, heating, lubricating, diagnosticsand control equipment), and fire suppression equipment. The firesuppression equipment can be located on a single chassis, or each onseparate chassis or any combination thereof for mobilization purposeswhich are mechanically or electrically connected while in operation toact as a single power generation unit.

In one example, the fuel source 46 can be a natural gas pipeline, CNG,LNG, or a well proximate the turbine 44. Combustion of the fuel in theturbine 44 in turn powers a generator 50 that produces electricity.Shaft 52 connects generator 50 to turbine 44. The combination of theturbine 44, generator 50, and shaft 52 define a turbine generator 53. Inanother example, gearing can also be used to connect the turbine 44 andgenerator 50. An example of a micro-grid 54 is further illustrated inFIG. 1, and which distributes electricity generated by the turbinegenerator 53. Included with the micro-grid 54 is an optional transformer56 for stepping up or down voltage of the electricity generated by thegenerator 50 to a voltage more compatible for use by electrical powereddevices in the hydraulic fracturing system 10.

A “split bus” (e.g, dual or triple, or more microgrid) or “single bus”(e.g., microgrid) electric hydraulic fracturing fleet may be availableto function with the present disclosure. As used herein, the microgridmay be an off-utility power grid that is closed circuit andself-contained. For example, the microgrid may include at least oneelectricity generator, one switch gear component, and one activeelectrical load. The microgrid may also be synced with the utility powergrid and pull additional power from the utility power grid. The utilitypower may be unable to provide all of the needed power for oilfieldhydraulic fracturing, drilling, intervention, and other oilfieldservices; and the use of the microgrid is to supplement or replace theutility power. The split or single bus use external switch gear trailerswhich are physically separate from the MPU to provide extra switch gear(e.g., breakers, relays, electrical buses) to allow electrical power tobe placed on a common bus (e.g., combining the power of two or moregenerators). The present disclosure, via at least FIGS. 3 to 9, providenovel packaging of the MPU and at least the switch gear to allow asavings on quantity of trailers and to reduce the complexity of theelectrical connections. Such a reduction may be by reducing a number ofinterconnecting power cables. This reduction in equipment will notreduce functionality but will improve mobilization times and simplicityof interfacing various components of the hydraulic fracturing system 10,while reducing space required on a well site as well as capital cost andmaintenance costs. In an example, such equipment may include hydraulicfracturing equipment that represents an electrical load addressed by theMPU of the present disclosure. As such the equipment can includehydraulic fracturing pumps, hydration units, chemical units, blenders,proppant storage, conveyer belts, lights, datavans, cranes, wirelineequipment, monitoring equipment, water pumps, compressors, heaters, andother supporting equipment.

The switch gear may be any gear such as breakers, switches, and relaysthat are used to control the distribution of electricity. Electricalsafety and diagnostics may also be provided by the switch gear. Each MPUmay include at least one large breaker for connecting and disconnectingits own generator from the electrical load. The MPUs may be limited inhow much switch gear can be integrated into its chassis due to size andweight requirements for mobility. Many times a separate electronicequipment room is used to supplement the generator to provide switchgear support or dedicated switch gear units (trailers, skids, bodyloadtrucks) are used to provide load sharing and greater distribution.

In another example, the power generated by the turbine generator and thepower utilized by the electrical powered devices in the hydraulicfracturing system 10 are of the same voltage, such as 4160 V so thatmain power transformers are not needed other than as isolationtransformers. In one embodiment, multiple 3500 kVA dry cast coiltransformers are utilized. Electricity generated in generator 50 isconveyed to transformer 56 via line 58. In another embodiment, a step-uptransformer is provided for transformer 56, where the secondary voltageof the step-up transformer is higher than its primary voltage. Such ausage may be advantageous for remote power transmission to limittransmission losses. In one example, transformer 56 steps the voltagedown from 13.8 kV to around 600 V. Other example step down voltagesinclude 4,160 V, 480 V, or other voltages. The output or low voltageside of the transformer 56 connects to a power bus 60, lines 62, 64, 66,68, 70, and 72 connect to power bus 60 and deliver electricity toelectrically powered end users in the system 10. In another example,line 62 connects fluid source 20 to bus 60, line 64 connects additivesource 24 to bus 60, line 66 connects hydration unit 18 to bus 60, line68 connects proppant source 32 to bus 60, line 70 connects blender unit28 to bus 60, and line 72 connects motor 39 to bus 60. In an example,additive source 24 contains ten or more chemical pumps for supplementingthe existing chemical pumps on the hydration unit 18 and blender unit28. Chemicals from the additive source 24 can be delivered via lines 26to either the hydration unit 18 and/or the blender unit 28. In oneembodiment, the elements of the system 10 are mobile and can be readilytransported to a wellsite adjacent the wellbore 12, such as on trailersor other platforms equipped with wheels or tracks.

FIG. 2 is an elevation schematic of example portions 200 of thehydraulic fracturing system 10 of FIG. 1. FIG. 1 particularlyillustrates some basic components of the hydraulic fracturing system 10at a wellbore site for providing electrical load sharing. An MPU 200includes a turbine generator 202 that may be supported by a natural gasturbine engine coupled to a three-phase, 60 hertz (Hz) electricgenerator to produce power as the turbine engine rotates. In analternative, the generator can generate electricity at 50 Hz, or at anyother frequency useful for hydraulic fracturing fleets. In theillustrated embodiment, the MPU includes components with referencenumerals 202, 204, 206, and 210. Reference numeral 202 is a turbinegenerator mounted within a trailer, for example. However, references tothe turbine generator are interchangeably used with reference to atrailer including these components, and the reference numeral 202. Thesame applies to reference numeral 204 providing an air intake filter, toreference numeral 206 providing an EER (sometimes referred to as acontrol trailer), and to reference numeral 210 providing a walk area. Assuch, the MPU is shown as including an electronic equipment room (EER)206, which can house wiring, breakers, controls, monitoring systems,fire suppression support, auxiliary transformers, and a battery bank forsecondary power when the turbine generator is not operating and there isno other power source. Some of the auxiliary components in the EER, suchas the fans, lube motors, valves, etc., as well as some of the supportequipment, such as gas compressors, gas heaters, and filtration systems,use lower voltage than what is generated. In an example, such lowervoltages may be 120V, 240V, and 480V. The auxiliary transformer, inanother example, is smaller than the fracturing pump step downtransformers. FIG. 1 also illustrates an air intake filter house 204that may be positioned on top of or adjacent to the MPU turbinegenerator arrangement 202, and a walk area 210 that may be connected tothe MPU turbine generator arrangement 202 and EER 206 to enablepersonnel access. The example portions 200 can be taken as an example ofan electrical microgrid.

In an example, the EER 206 may include other components than recitedabove and may be named differently but performs the general functionsnoted above. For example, the EER 206 is a support unit that may be partof the MPU and may include communications, switch gear, firesuppression, motor control center (MCC) for auxiliary loads, technicianmonitoring space, battery backups for critical auxiliary equipment,transformers, air compressors, and data monitoring/recording. The MPUmay have a dedicated trailer for these components alone, while otherhave parts of this may be integrated into the generator spaces of theMPU.

In some examples, the battery bank of the EER 206 can power lighting,fire suppression, emergency turbine lube pumps, and onboard electronics.A switch gear trailer 208 may provide output 212 for power distribution,high voltage breakers, and “lock-out, tag-out” capabilities. “Lock-out,tag-out” is an understood safety procedure to ensure that dangerousmachines are properly shut off and not able to be started up again priorto the completion of maintenance or servicing work.

FIG. 3 is an end perspective view of an example of a mobile platform 300that includes one or more mobile power units (MPUs) that is integratedto or with switch gear components, according to embodiments in thepresent disclosure. As such, the mobile platform 300 includes switchgear and MPU components within trailer 304. While the drawings provide asingle trailer to demonstrate that the MPU components reside within thesingle trailer with the switch gear components, this is merely forillustrative purposes. The integration may be by components of theswitch gear physically or electrically coupled between and throughoutthe components for the MPUs. As such, the reference to trailer 304 ismerely illustrative to indicate at least where the substantialcomponents for these units may be located.

At least one first switch gear integrated in the MPU provides electricaloutput connections 302 a-c to handle electric power from at least oneturbine generator in the trailer 304. The MPUs, therefore, include areafor the switch gear, and include the at least one turbine generator thatis configured to output a voltage that matches the requirements of loadcomponents. In addition, multiple MPUs may be coupled together on acommon electrical bus such that a combined electrical current generatedas a result of the voltage from the multiple MPUs drives current throughthe common bus to the components of the hydraulic fracturing system.Example configurations to support such a voltage requirements withcurrent capabilities are provided in FIGS. 4-9. Further, the hydraulicfracturing system of the present disclosure may include electricalfracturing equipment in a separate trailer or on the ground by thewellbore with at least one second switch gear to support the at leastone first switch gear providing electrical output connections 302 a-cfor handling electric power from the MPU in trailer 304, and also, fromother MPUs, using a common bus, for instance. A datavan (a separatemobile platform) for data may be included in the system for loadshedding, load sharing, and power distribution for the electricalfracturing equipment comprising the at least one second switch gear. Assuch, a datavan is, herein, referring to a trailer housingcommunications and controls for all of fracturing system and to enablehydraulic fracturing operations where a focus of the operations is onthe wellhead and fluid pumping instead of power generation. The loadshedding system may also include load-inhibit functionality to prevent apump operator from running a pump or system of pumps and other equipmentat a higher load level than power can be supplied. In addition, the loadshedding system may also take action to drop one or more loads in apredetermined sequence to ensure that the hydraulic fracturing system isnot overloaded. In another example, the load shedding system may reducethe rate of pumps and other equipment that are loaded to the hydraulicfracturing system. The reduction of the load in this manner is analternative to fully shutting off the pumps and the other equipment.

FIG. 4 is an elevation schematic of portions 400 of a hydraulicfracturing system in accordance with one example configuration of thepresent disclosure. MPUs 402 a-c include single or multiple turbinegenerators 410 a-c and switch gear 412 a-c, which are illustrated asdirectly powering fracturing pump trailers or units (FPs) 404 a-f. Inthis example configuration, separate switch gear equipment or common busis not provided. Each respective switch gear (breakers or relays) 412a-c is integrated into each respective trailers 402 a-c formingintegrated MPUs. Power cable connections 408 a-c are provided totransmit power from the turbine generators 410 a-c integrated with or tothe switch gear 412 a-c, shown by dotted lines connecting the boxes410-412. This may be the case in each trailer or mobile platform formingMPU 402 and couple to the respective FPs 404 a-f. Even though thedrawings provide the MPU as including the turbine generators and theswitch gear as two separate reference numerals 410 and 412 forillustrative purposes, a person of ordinary skill would recognize thatthese are integration in physical layout or connectivity. This is alsothe case for the other example configurations provided herein. Inaddition, transformers may be used between each respective FP 404 andswitch gear 412 combination of the embodiment in FIG. 4 to condition thepower for use by the fracturing equipment.

Due to the integrated switch gear of this example configuration, theMPUs 402 including the turbine generators 410 a-c, may have a smallerpower output and can only power a limited number of FPs. Walkways 406a-c are available to access the integrated MPUs and switch gear. Theturbine and generator components are downgraded from traditional usageand a single trailer used for the integrated MPU is a heavy duty trailerthat includes three or more axles. In example, instead of a traditionalfour 5.7 MW turbine generator configuration, an integrated MPU may useintegrated switch gear with five 5 MW turbine generators. Theintegration and elimination of the EER and Switch Gear are beneficial toreduce complexity and to promote reliability of a new configuration aspresently disclosed. As such, the at least one switchgear used in anyembodiment may be physically arranged to replace an EER of at least onemobile unit that may have been designed to include the EER. In addition,an MPU that is integrated with the switch gear in a single trailereliminates the requirement for the walkway 406 as well. As such, thepresent embodiments merely illustrate the walkways for exemplarypurposes. Further, MPUs 402, may include multiple turbine generators 410a and switch gear 412 a. Without a common bus, power cannot bedistributed to or from other MPUs. As such, FIG. 4 illustrates each MPU402 as powering two separate FPs, but it is possible to power a singleFP, or multiple FPs depending on the integrated switch gear and powerrequirements of each pump (or conversely, the power output of each MPU402 a-c). While the reference to an MPU is generally made, the referencemay be to a single MPU of a single trailer 402 a, b, or c, or tomultiple MPUs in each of the single trailers 402 a, b, and c. Differenthydraulic horsepower requirements are provided and MPU/FP matches areidentified for so that they can be added or removed for a modular set upbased on specific needs.

FIG. 5 is an elevation schematic of portions 500 of a hydraulicfracturing system in accordance with another example configuration ofthe present disclosure. Here, the example reference numerals areprovided for at least one MPU 502 a and FPs 504 a,b combination, but aperson of ordinary skill would recognize that the description supportingthe example reference numerals are available to the other combinationsof the mobile platforms 502 b,c and FPs 404 c-f. In this configuration,power cable interconnects 514 a,b are provided between the MPUs 502 a-cto act as a common bus for load sharing. As in the prior configuration,optional walkways 506 are provided for personnel access. Power cableconnections 508 are provided to transmit power from the turbinegenerator 510 integrated with the switch gear 512 to the respective FPs504 a-f. Extra components (e.g., fuses, switches, etc.) in switch gear512 and larger internal busses are additionally provided, as requiredand as discussed herein, to handle higher electrical loads than a singleMPU can output. Communications between turbine control systems(computers) are also provided, as required, to support redundancy inthis configuration. As such, a configuration as in FIG. 5 allows theswitch gear, interconnect cables, and electrical bus bars are sized tohandle all of the available electrical current that can be generated bythe combined MPUs.

Alternatively, the sizing is in accordance with a selective use ofinterconnects for just portions of the system components. Such portionsare determined based at least in part on the load ratings provided forthe components. In this process, when the selective use is applied,controls are provided to open or close the load sharing switch gear forprotection against overcurrent situations. Switches, fuses, and otherfailsafe components understood to handle overcurrent situations areavailable in the present disclosure to work with the switch gear. With acommon bus 514, it is also possible to apply a load shedding controlsystem which can shutdown (e.g., using a stop command) or which can opena breaker for FPs 504 if the power demand exceeds the available powerproduction. This can happen if extra fluid rate is needed or if wellheadpressure increases unexpectedly, or if an MPU fails. The presentdisclosure also anticipates that a turbine can fail and electrical loadwill need to be lowered immediately to prevent the other MPUs from overloading and shutting down for protection. The additional components ofthe integrated switch gear supports and resolve such issues.

FIG. 6 is an elevation schematic of portions 600 of a hydraulicfracturing system in accordance with yet another example configurationof the present disclosure. Here, like the prior example, the referencenumerals are only provided for at least one MPU 602 a and FPs 604 a,bcombination, but a person of ordinary skill would recognize that thedescription supporting the example reference numerals are available tothe other combinations of the MPUs 602 b,c and FPs 604 c-f. In thisconfiguration, power cable interconnects 614 a-e are provided between aVFD (Variable Frequency Drive)/MCC (Motor Control Center) compartment ofthe FP 604 a-f instead of on the areas for the turbine generator 610 ineach of the MPUs 602 a-c. As in the prior configuration, optionalwalkways 606 are provided for personnel access. Power cable connections608 are provided to transmit power from the MPUs 602 (with integratedswitch gear 612 and turbine generator 610) to the respective FPs 604a-f. Extra components (e.g., fuses, switches, etc.) in switch gear 612and the VFD/MCC and larger internal busses are additionally provided, asrequired and as discussed herein, to handle higher electrical loads thana single MPU can output.

This example configuration bears similarities to the exampleconfiguration of FIG. 5. A difference in this example is that extra loadsharing switch gear for the common bus 614 will be in a VFD/MCCcompartment of the FP 604 instead of in the area for the turbinegenerator 610 of the MPU 602. Further, it may not be essential for allinterconnecting cables to be used, as long as the fracturing pumptrailers 604 are in electrical communication with a source of electricpower, a single interconnect will suffice. For example, FP 604 a,b doesnot need to have an interconnect 614 a, or FP 604 e may not need to havean interconnect 608 with MPU 602 c in the illustrated mobile platform aslong as it can share power from FP 604 d or FP 604 f. In this and any ofthe embodiments, at least one VFD at least one MCC is provided onindividual ones of the one or more external mobile units of theembodiments, such that these components, via the one or more externalmobile units, is therefore, physically external relative to the mobileunit—such as the MPU 602—hosting the generator and switchgear. However,extra load sharing switch gear may be in the one or more external mobileunits.

FIG. 7 is an elevation schematic of portions 700 of a hydraulicfracturing system in accordance with further example configurationsavailable in the present disclosure. In this example, a single MPU/FPsystem is provided. In an example, the FP 704 is a single trailer forfracturing pumps 704 a,b. As such, fracturing pumps and fracturing pumptrailers are used interchangeably throughout this disclosure. In FIG. 7,the example configuration provides separate transformer skids 706 a,bused to step up or step down the voltage for the FP 704 a,b. Thetransformer in transformer skids 706 a,b can also be an isolationtransformer for filtering out harmonics between the power source(generators) and the load (fracturing equipment in FP 704 a,b) with orwithout changing the voltage. The switch gear 712 is still integratedwith the turbine generator 710 and an external switch gear unit may notnecessarily be used to act as a common bus or for power distribution.Power cable connections or interconnects 708 a,b,c,d are provided totransmit power from the turbine generators 710 that are integrated tothe switch gear 712 in the MPU to the respective FPs 704 a-f via thetransformer skids 706 a,b. Interconnects may be implemented in thisexample as in the examples from FIGS. 5 and 6. A person of ordinaryskill would recognize that the embodiments in each of the exampleconfigurations may be used interchangeably based on the disclosureherein. As such, one or more power cable interconnects may be configuredto couple the mobile unit with a second mobile unit of one or moreexternal mobile units in this and other embodiments. The second mobileunit has at least one second generator and at least one second switchgear and the one or more cable interconnects then enable transmission ofpower in support of redundancy or load sharing between the mobile unitand the second mobile unit.

The embodiment of FIG. 7 also supports a second implementation where theMPU 702 includes turbine generator 710 and integrated switch gear 712 soas to provide power to one or more pieces of FP equipment in FP unit704, but the layout of the equipment may be different from the layout ofthe prior implementation, above, using FIG. 7. For example, in thissecond implementation using the layout in FIG. 7, the transformer oftransformer skid 706 a,b (if required) may include a VFD (VariableFrequency Drive) and possibly an MCC (Motor Control Center). As such,the VFD and MCC are on a different separate trailer than the FP 704.This design may allow large fluid pumps to be better positioned relativeto wellheads on wellsites, when space is limited. Thesetransformer/VFD/MCC support trailers 706 (in such an embodiment) areherein referred to as Auxiliary Trailers.

FIG. 8 is an elevation schematic of portions 800 of a hydraulicfracturing system according to other example configurations of thepresent disclosure. This embodiment illustrates load sharing between thetransformer skids 806 b,c. The remaining reference numerals 802 a,b,810, 812, 808 a,b,c,d, 806 a, and 804 a,b read on similar components orfunctions from the corresponding reference numerals in FIG. 7—i.e., 702a,b, 710, 712, 708 a,b,c,d 706 a, and 704 a,b. As such, the samediscussion from FIG. 7 applies to these components. In addition, in FIG.8, extra switch gear will need to be integrated into the transformerskid 806 b,c which will create a larger skid and will take up more room,or the transformer in the transformer skid 806 b,c will need to bedowngraded to be smaller, in effect limiting the horsepower of theattached FP unit 804 b,c. In this example, load sharing can be on theincoming side of the transformer or the outgoing side (secondaryvoltage). When the load sharing takes place on the incoming side, theswitch gear, bus bars, and cable interconnects is sized based in part onthe current available at the generated voltage. When the load sharingequipment is on the outgoing side (e.g., when it can be stepped up orstepped down) then the switch gear, bus bars, and cable interconnectsare sized based in part on the current available on the secondary sideof the transformer.

In an example, when an interconnect is provided between transformers ofat least two mobile units of the one or more external mobile units, asin the embodiment of FIG. 8, then the interconnect for load sharingbetween the transformers can be configured based at least in part oncurrents available from a secondary side of the transformer. Forexample, at least one load sharing switch gear is provided that isoptionally associated with at least one of the transformers andconfigured for load sharing on an incoming side of the at least one ofthe transformers. This arrangement is such that the at least one loadsharing switch gear, associated bus bars, and associated cableinterconnects are sized based at least in part on current available fora voltage output of a secondary side of the of the at least one of thetransformers. In an alternative or together with the above load sharingexample, when the at least one load sharing switch gear is configuredfor load sharing on an outgoing side of the at least one of thetransformers, a different arrangement may be provided. The differentarrangement is such that the at least one load sharing switch gear, theassociated bus bars, and the associated cable interconnects are sizedbased at least in part on the current available at the secondary side ofthe transformer.

FIG. 9 is an elevation schematic of portions 900 of a hydraulicfracturing system according to further example configurations availablein the present disclosure. This embodiment illustrates load sharingtaking place on the FP units 904 b,c. The remaining reference numerals902 a,b, 910, 912, 908 a,b,c,d, 906 a, and 904 a,b read on similarcomponents or functions from the corresponding reference numerals inFIG. 8—i.e., 802 a,b, 810, 812, 808 a,b,c,d 806 a, and 804 a,b. As such,the same discussion from FIGS. 7 and 8 applies to these components. Whenthe FP 904 b,c have onboard VFD/MCC rooms or compartments, it may bepossible to add extra switch gear for load sharing in those rooms. Theload sharing will be on the secondary side of the transformer intransformer skid 906 a-c. For example, if the transformer in transformerskid 906 a-c is stepping the voltage down from 13,800V to 600V, theelectrical current requirements will be higher than required if this wasnot the case. While this may not be ideal current requirements, and willrequire larger load sharing gear, this implementation saves space on theMPUs 902 at the cost of consuming space on the FP 904, which may bepreferable in some cases. In this embodiment, a datavan can possiblyperform the load shedding control duties instead of the MPUs 910. Aspreviously noted, datavan is a trailer housing communications andcontrols for all of the FP equipment for hydraulic fracturing operationswhere the focus is on the wellhead and fluid pumping instead of powergeneration. All FP equipment communicate with the datavan for control,when load sharing switch gear is onboard the FP 904, it can becontrolled from the datavan instead of the MPU 910.

FIG. 10 is an elevation schematic of portions 1000 of a hydraulicfracturing system according to yet another example configurationavailable in the present disclosure. In this embodiment, a configurationand associated method is provided for load sharing where the AuxiliaryTrailers 1006 b,c (such as described in the alternate embodiment of FIG.7) houses extra load sharing gear. This configuration saves space on theMPUs 1002 and will allow the load sharing to be on the high voltage sideof the transformer. The remaining reference numerals 1002 a,b, 1010,1012, 1008 a,b,c,d, 1006 a,d and 1004 a,b read on similar components orfunctions from the corresponding reference numerals in FIG. 9—i.e., 902a,b, 910, 912, 908 a,b,c,d 906 a, and 904 a,b. As such, the samediscussion from FIGS. 7, 8, and 9 applies to these components. When astep up transformer is used in this embodiment, the load sharing cantake place on the secondary side—similarly discussed with respect toFIG. 7. When a step down transformer is used, the load sharing can takeplace on the primary side. This process also maintains all of theelectrical gear off of the FP trailers 1004. Only one load sharinginterconnect 1014 is illustrated for simplicity, but in reality, theAuxiliary Trailers 1006 b,c can have as many load sharing breakers asneed to form as common bus. In many situations, two interconnects may besufficient, but it is feasible to maintain more available interconnectsto simplify interconnecting cable layouts or to electrically bypassfailed equipment. Electrical load sharing may be preferable at highervoltages due to the current (amperage) requirements being smaller,therefore smaller cables and switch gear can be used.

In addition, many of the above embodiments show additional switch gearintegrated into the MPU to allow load sharing between MPUs for a commonbus. In these embodiments, a large three phase power cable may beinterconnected between the load sharing switch gear to any adjacent MPUsintegrated with other load sharing switch gear. However, the extra gearand a larger internal bus that may be needed to carry the higherelectrical current will require compensation in the form of the turbineengines and generators being even smaller to allow mobility of thesystem.

The above embodiments may be combined in any manner as is readilyapparent to a person of ordinary skill reading the present disclosure.In the above embodiments and any combinations therefrom, at least onefracturing pump (FP) mobile unit may be provided as part of one or moreexternal mobile units. The at least one FP mobile unit is physicallyexternal relative to the mobile unit having a generator and switch gearfor generating power for the at least one FP mobile unit. Further, apredetermined number of FP mobile units include in the one or moreexternal mobile units may be determined for the system describedthroughout this disclosure. The predetermined number of FP mobile unitsmay be determined by a maximum of the power available from the at leastone generator and handled by the at least one switch gear.

In a further example, a predetermined number of generators including theat least one generator may be determined for the system of the presentdisclosure. In an aspect, the predetermined number of generators isdetermined such that each of the predetermined number of generators hasa power output value that is lesser than a power output of an isolatedsingle generator occupying all available space in an independent mobileunit physically external to the mobile unit. As the generator and switchgear are being integrated to a singular and integrated mobile unit, thespace is limited and lower rating equipment may be provided instead.Other embodiments to the above embodiments allow for extra integratedswitch gear for a common bus integrated into the FP trailers or with anexternal transformer and/or VFD skids—i.e., in the Auxiliary Trailers.This extra integrated switch gear may require additional spaceconsumption which may force the FP trailer to incorporate equipment withlower hydraulic horsepower rating due to smaller motors/pumps to allowall of these components to fit onto a mobile platform. Further, largethree phase cables, or multiple single phase cables can be used forelectrical power interconnects. The above embodiments are described ascapable of supporting several common voltages, such as 25 KV, 13.8 KV,6.6 KV, 4160V, 2000V, 600V, 690V, 480V, all at +/−5%. However, anyvoltage is feasibly based on the capabilities of the generators used andon the ratings of the components requiring the generated power. For loadsharing capabilities, higher voltage may be better appreciated andissues may arise with voltages below 5,000V. While it may not bepossible to practically size switch gear, bus bars, and interconnectingcables to be able to handle the electrical current for an entirefracturing fleet at voltages below 5,000V to form a common bus, minorload sharing between two individual pumps (FP units) may still bepossible even at low voltages.

The technology herein can be used for equipment where the voltage isconstant, such as when the load operates at the same voltage as thegenerated voltage. Alternatively, the technology and equipment hereincan be used where step up or step transformers are used to alter thevoltage for the attached load (FP units). Examples of components in theFP units include blenders, hydration units, chemical units, proppantequipment, lights, auxiliary water pumps, monitoring equipment, datacollection offices, personnel trailers, cranes, gas compressionequipment, gas filtering equipment, heating equipment, and other thirdparty equipment that is used on well sites.

FIG. 11 is a flowchart 1100 of a hydraulic fracturing method using toexample configurations of the embodiments herein. The method includes asub-process 1102 for providing a mobile unit with at least one generatorand at least one switchgear, such as a system as described above. The atleast one generator is coupled to the at least one switch gear on themobile unit. The method includes sub-process 1104 for generating powerfrom the at least one generator. The system may be part of a hydraulicfracturing system that consumes the power and that includes a wellboreand at least one pressuring system to create fractures in a subterraneanformation that surrounds the wellbore. A verification is performed viasub-process 1106 for the power generated being sufficient to drive atleast one load of the one or more external mobile units. When suchverification is positive, sub-process 1108 provides the power inelectrical busses for at least one load in the one or more externalmobile units. Power may be generated via sub-process 1104 till thecapacity is achieved if the verification in sub-process 1106 isnegative.

The present invention described herein, therefore, is well adapted tocarry out the objects and attain the ends and advantages mentioned, aswell as others inherent therein. While a presently preferred embodimentof the invention has been given for purposes of disclosure, numerouschanges exist in the details of procedures for accomplishing the desiredresults. For example, other the recesses can be put into arrangementsother than those described, such as all being in a vertical or otherarrangement. These and other similar modifications will readily suggestthemselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims.

In the various embodiments of the disclosure described, a person havingordinary skill in the art will recognize that alternative arrangementsof components, units, conduits, and fibers could be conceived andapplied to the present invention.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Examples of computer-readable medium used in the datavan and in thecommunications achieved in the present embodiments can include but arenot limited to: one or more nonvolatile, hard-coded type media, such asread only memories (ROMs), CD-ROMs, and DVD-ROMs, or erasable,electrically programmable read only memories (EEPROMs); recordable typemedia, such as floppy disks, hard disk drives, CD-R/RWs, DVD-RAMs,DVD-R/RWs, DVD+R/RWs, flash drives, memory sticks, and other newer typesof memories; and transmission type media such as digital and analogcommunication links. For example, such media can include operatinginstructions, as well as instructions related to the systems and themethod steps described previously and can operate on a computer. It willbe understood by those skilled in the art that such media can be atother locations instead of, or in addition to, the locations describedto store computer program products, e.g., including software thereon. Itwill be understood by those skilled in the art that the various softwaremodules or electronic components described previously can be implementedand maintained by electronic hardware, software, or a combination of thetwo, and that such embodiments are contemplated by embodiments of thepresent disclosure.

What is claimed is:
 1. A system comprising: a first mobile unit; atleast one switch gear to be associated with at least one transformer, aninterconnect, and a bus bar; and at least one first generator coupled tothe at least one switch gear and located on the first mobile unit withthe at least one switch gear, the first mobile unit configured toprovide power generated by the at least one first generator usingelectrical buses of the at least one switchgear and using the at leastone transformer, the interconnect, and the bus bar, the power for loadson one or more external mobile units, the at least one switchgear, theelectrical buses, the interconnect, and the bus bar sized to supportvoltage and current requirements of the loads and to support voltage andcurrent outputs of the at least one transformer with the at least onefirst generator in a load sharing arrangement with a second generator ofa second mobile unit.
 2. The system of claim 1, wherein the system ispart of a hydraulic fracturing system that consumes the power and thatcomprises a wellbore and at least one pressuring system to createfractures in a subterranean formation that surrounds the wellbore. 3.The system of claim 1, further comprising: at least one fracturing pump(FP) mobile unit of the one or more external mobile units, the at leastone FP mobile unit physically external relative to the first mobileunit, wherein the at least one transformer is provided to condition thepower supplied to the at least one FP mobile unit.
 4. The system ofclaim 1, further comprising: a predetermined number of FP mobile unitscomprised in the one or more external mobile units, the predeterminednumber of FP mobile units determined by a maximum of the power availablefrom the at least one first generator and handled by the at least oneswitch gear.
 5. The system of claim 1, further comprising: apredetermined number of first generators comprising the at least onefirst generator, the predetermined number of first generators havingindividual power output values that is lesser than a power output of anisolated single generator occupying all available space in anindependent mobile unit physically external to the first mobile unit. 6.The system of claim 1, further comprising: the at least one switchgearbeing physically arranged to replace an electronic equipment room (EER)of at least one of the one or more external mobile units that isdesigned to comprise the EER.
 7. The system of claim 1, furthercomprising: at least one Variable Frequency Drive (VFD); and at leastone Motor Control Center (MCC), the VFD and the MCC being on individualones of the one or more external mobile units that is physicallyexternal relative to the first mobile unit.
 8. The system of claim 1,further comprising: the interconnect configured to couple the firstmobile unit with the second mobile unit, the second mobile unit havingat least one second switch gear in addition to the second generator, theinterconnect to transmit power in support of redundancy in addition tothe load sharing arrangement between the first mobile unit and thesecond mobile unit.
 9. The system of claim 1, further comprising: the atleast one switch gear configured in the load sharing arrangement bybeing in part on an incoming side of the at least one transformer suchthat the sizing is based at least in part on current available for thevoltage output of a secondary side of the at least one transformer thatis coupled to the at least one first generator and the second generator;or the at least one switch gear configured in the load sharingarrangement by being in part on an outgoing side of the at least one ofthe at least one transformer such that the sizing is based at least inpart on the current available at the secondary side of the at least onetransformer that is coupled to the at least one first generator and thesecond generator.
 10. The system of claim 1, further comprising: atleast one load sharing FP mobile unit coupled, as at least one of theloads, with a second FP mobile unit of the one or more external mobileunits; and a datavan in the one or more external mobile units forcontrol of the at least one load sharing FP mobile unit, the datavanoffering the control of the at least one load sharing FP mobile unitinstead of a second control available from within the first mobile unit.11. The system of claim 1, further comprising: the at least onetransformer being an isolation transformer that is located in the one ormore external mobile units, the isolation transformer being physicallyexternal relative to the first mobile unit and being configured forfiltering harmonics between the at least one first generator and theloads in the one or more external mobile units.
 12. A method comprising:providing a first mobile unit with at least one first generator and atleast one switchgear located together in the first mobile unit, the atleast one first generator coupled to the at least one switch gear on thefirst mobile unit, the at least one switch gear to be associated with atleast one transformer and with an interconnect and a bus bar; generatingpower from the at least one generator; providing the power usingelectrical buses of the at least one switchgear and using the at leastone transformer, the interconnect, and the bus bar, the power for loadsin one or more external mobile units, the at least one switchgear, theinterconnect, the bus bar, and the electrical buses sized to supportvoltage and current requirements of the loads and to support voltage andcurrent outputs of the at least one transformer with the at least onefirst generator in a load sharing arrangement with a second generator ofa second mobile unit.
 13. The method of claim 12, further comprising:providing at least one fracturing pump (FP) mobile unit of the one ormore external mobile units that is physically external relative to thefirst mobile unit; and conditioning the power supplied to the at leastone FP mobile unit using the at least one transformer.
 14. The method ofclaim 12, further comprising: determining a number of FP mobile unitsfor the one or more external mobile units based at least in part on amaximum of the power available from the at least one first generator andhandled by the at least one switch gear.
 15. The method of claim 12,further comprising: determining a number of generators for the at leastone first generator based at least in part on the number of firstgenerators having individual power output values that is lesser than apower output of an isolated single generator occupying all availablespace in an independent mobile unit physically external to the firstmobile unit.
 16. The method of claim 12, further comprising: physicallyarranging the at least one switch gear to replace an electronicequipment room (EER) of at least one of the one or more external mobileunits that is designed to comprise the EER.
 17. The method of claim 12,further comprising: providing at least one Variable Frequency Drive(VFD); and providing at least one Motor Control Center (MCC), the VFDand the MCC being on individual ones of the one or more external mobileunits that is physically external relative to the first mobile unit. 18.The method of claim 12, further comprising: coupling the first mobileunit with the second mobile unit using the interconnect, the secondmobile unit having at least one second switch gear in addition to thesecond generator, the interconnect to transmit power in support ofredundancy in addition to the load sharing between the first mobile unitand the second mobile unit.
 19. The method of claim 12, furthercomprising: coupling at least one load sharing FP mobile unit to sharethe at least one load of a second FP mobile unit of the one or moreexternal mobile units; and controlling, via a datavan in the one or moreexternal mobile units, the at least one load sharing FP mobile unit, thedatavan offering the control of the at least one load sharing FP mobileunit instead of a second control available from within the first mobileunit.
 20. The method of claim 12, further comprising: filteringharmonics between the at least one first generator and the loads in theone or more external mobile units using an isolation transformer as theat least one transformer that is in the one or more external mobileunits, the isolation transformer being physically external relative tothe first mobile unit.